Patent Application
20140169135
This application claims the benefit of Israeli patent application No. 214575 filed on 9 Aug. 2011 which is incorporated herein by reference.
The present invention relates to method and system for detecting an intrusion in a confined space and the implementation thereof.
It is known in the art to apply the Doppler principle in alarm systems for detection of intrusion. In devices of this type, radiation is emitted by a transmitter and is reflected by objects, including people. The reflected radiation is picked up by a receiver and evaluated. If the reflection results from an object at rest, the frequency of the received radiation coincides with the frequency of the transmitted radiation. If, however, the reflection results from an object which is moving with a velocity component in the direction of the transmitter and/or the receiver, or away from the transmitter or receiver, then a Doppler frequency shift occurs in the received radiation.
It is also known that an intrusion into a confined space, for example by breaking a window or a wall, generates a low frequency signal along with a Doppler frequency shift.
Known alarm systems utilize ultrasonic radiation in a frequency range of about 40 kHz, for example. However, ultrasonic devices have special disadvantages. One particular disadvantage is that the transmitted ultrasonic radiation is also influenced, for example, by moving air, for instance by attenuation fluctuations. Particularly in heated areas, however, air turbulence cannot be precluded.
In order to avoid false alarms, there is provided an alarm system in which one section that operates with low frequency radiation and another section that operates with ultrasonic waves. In this system it has been found that false alarms can be reduced or even totally avoided, if an alarm is given only when there is a coincidence, namely when an occurrence which is to be reported is detected by both sections; or even more preferably, if an alarm is given only when an occurrence which is to be reported is first detected by a section which operates with low frequency radiation and if said occurrence is detected by both sections.
In accordance with a first aspect of the present invention, there is provided a method for determining an alarm condition, the method characterized by the steps of:
generating an ultrasonic acoustic signal and transmitting it into a confined space; and
detecting a LF acoustic signal and an ultrasonic acoustic signal with a Doppler shift, said signals being indicative of the intrusion; and
determining whether said LF acoustic signal and said ultrasonic acoustic signal with a Doppler shift were detected within an assigned timeframe; and
generating an alarm signal, if said LF acoustic signal and said ultrasonic acoustic signal with a Doppler shift were detected within an assigned timeframe.
In accordance with a second aspect of the present invention, there is provided a method for determining an alarm condition, the method characterized by the steps of:
generating an ultrasonic acoustic signal and transmitting it into a confined space; and
detecting a LF acoustic signal and an ultrasonic acoustic signal with a Doppler shift, said signals being indicative of the intrusion; and
determining whether said LF acoustic signal was detected before said ultrasonic acoustic signal with a Doppler shift; and
determining whether said LF acoustic signal and said ultrasonic acoustic signal with a Doppler shift were detected within an assigned timeframe; and
generating an alarm signal, if said LF acoustic signal was detected before said ultrasonic acoustic signal with a Doppler shift and said LF acoustic signal and said ultrasonic acoustic signal with a Doppler shift were detected within an assigned timeframe.
In accordance with a third aspect of the present invention, there is provided a detection system, the detection system is characterized by:
an ultrasonic transmitting unit arranged to generate and to transmit an ultrasonic acoustic signal into a confined space; and
an ultrasonic receiving unit arranged to receive and to detect an ultrasonic acoustic signal having a Doppler shift and to generate an electrical signal indicative of said Doppler shift; and a LF unit arranged to detect a LF acoustic signal and to generate an electrical signal indicative of said LF acoustic signal; and
a processing unit arranged to receive from said ultrasonic receiving unit an electrical signal indicative of the acoustic signal with a Doppler shift and from said LF unit an electrical signal indicative of the LF acoustic signal, said processing unit is configured to generate an alarm signal if said electrical signal indicative of the LF acoustic signal and said electrical signal indicative of the acoustic signal with a Doppler shift were received within an assigned time frame.
In accordance with a fourth aspect of the present invention, there is provided a detection system, the detection system is characterized by:
an ultrasonic transmitting unit arranged to generate and to transmit an ultrasonic acoustic signal into a confined space; and
an ultrasonic receiving unit arranged to receive and to detect an ultrasonic acoustic signal with a Doppler shift and to generate an electrical signal indicative of said Doppler shift; and
a LF unit arranged to detect a LF acoustic signal and to generate an electrical signal indicative of said LF acoustic signal; and
a processing unit arranged to receive from said ultrasonic receiving unit an electrical signal indicative of the acoustic signal with a Doppler shift and from said LF unit an electrical signal indicative of the LF acoustic signal, said processing unit is configured to generate an alarm signal if said electrical signal indicative of the LF acoustic signal was received before said electrical signal indicative of the acoustic signal with a Doppler shift and said electrical signal indicative of the LF acoustic signal and said electrical signal indicative of the acoustic signal with a Doppler shift were received within an assigned timeframe
Further aspects and advantageous features of the present invention are as described in the appended claims.
Exemplary embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
The ultrasonic acoustic signal is reflected by objects within the protected space and its frequency is shifted by objects within the space that are in motion, i.e. intruders (Doppler shift). An ultrasonic receiving unit 10 detects any reflected and frequency shifted ultrasonic acoustic signals and generates an electrical signal which is indicative of the Doppler shift of these signals. The ultrasonic receiving unit 10 of the preferred embodiment of the present invention comprises an ultrasonic acoustic receiver 11 that receives a reflected and frequency shifted ultrasonic acoustic signal. The output of said receiver 11 is then further amplified by a selective amplifier 12. The amplified signal is then inputted into a phase detector 13, that also receives an input from the frequency generator 23. The subtracted signal from the phase detector 13 is further filtered by a low pass filter 14, preferably with a cut-off frequency of 1 kHz. The filtered signal is actually a signal having the Doppler Effect frequency. This signal is then amplified by a low frequency amplifier 15 and digitized by means of an AID converter 16 prior to being further processed by a processing unit 40.
The system 100 also comprises a low frequency (LF) unit 30 which detects low frequency acoustic signals generated by intruders, for example low frequency acoustic signals generated by breaking a window or a wall, and generates an electrical signal that is further processed by the processing unit 40. The LF unit 30 of the preferred embodiment of the present invention comprises a low frequency acoustic microphone 31 that receives low frequency acoustic signals, indicative of an intrusion into the protected space. The output of said LF microphone 31 is then amplified by an amplifier 32 and further filtered by a low pass filter 33, preferably having a cut-off frequency of 100 Hz. This signal is then amplified by a low frequency amplifier 34 and digitized by means of an A/D converter 35 prior to being further processed by the processing unit 40.
The processing unit 40 comprises a programmable microcontroller 41 which is connected to the A/D converter 16 of said ultrasonic receiving unit 10 and to the A/D converter 35 of said LF unit 30. Said processing unit 40 receives input signals from the ultrasonic receiving unit 10 and from the low frequency unit 30. The microcontroller 41 is configured according to the preferred embodiment of the present invention to determine whether said input signals were detected within an assigned time period and to generate an alarm signal 42, only if both of said received input signals were received within an assigned time period, wherein said time period is preferably less than 2 seconds, and more preferably is less than 1 second, and even more preferably is less than 0.5 second.
According to another preferred embodiment of the present invention, the microcontroller 41 is configured to determine if an input signal from the low frequency unit 30 was received before an input signal from the ultrasonic receiving unit 10 and to determine if both of said received input signals were detected within an assigned time period, and to generate the alarm signal 42 only if the input signal from said low frequency unit 30 was received before the input signal from said ultrasonic receiving unit 10 and both of said received input signals were detected within an assigned time period, wherein said time period is preferably less than 2 seconds, and more preferably is less than 1 second, and even more preferably is less than 0.5 second.
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Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 214575 | Aug 2011 | IL | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IL2012/000285 | 7/23/2012 | WO | 00 | 1/29/2014 |
